Level 5: Systems. An organ system is a group of specialized organs working together to acheive a specific function.

Level 6: Organism. All the systems combined make of the organism (human). The organism continuously fine tunes itself to restore balance (homeostasis). Anything that stresses the body creates a need for adaptation, meaning the cells are not working optimally at that level.

Define pH and describe the scale used for pH

pH stands for Power of Hydrogen. It represents the acidity or alkalinity of a substance. The more hydrogen (H+) the more acidic, the more hydroxide (OH-) the more alkaline. A balance is neutral. The scale runs from 0-14, with 0 as pure acide and 14 as pure alkalinity.